1. Field of the Invention
The present invention relates to the field of mechanical engineering and electrical engineering and can be used advantageously particularly in automotive engineering and is directed especially to a method and a device for monitoring an electric motor drive unit for a drivable adjusting element, particularly a windowpane or a sunroof, in which the force of the drivable element is monitored for the realization of anti-trap protection.
2. Description of the Background Art
In electric window lifters of motor vehicles, for example, such an anti-trap protection is stipulated that assures that during closing of a vehicle window within the scope of automatic closure the counterforce to be overcome by the drive is monitored and limited in such a way that trapped objects can be acted upon only by the maximum allowable force (of typically 100 N) and otherwise the drive is automatically stopped and/or reversed.
Conventional electric window lifters in motor vehicles are designed, for example, as cable window lifters, as shown in DE 10 2010 013 597 B3. A rotating electric motor with a worm gear is shown therein, which drives a cable drum in two drive directions. The cable guided over the cable drum is guided by means of deflection rollers in such a way that it drives a follower, which is guided substantially perpendicular in a guide rail and for its part is connected to a windowpane, in the up and down direction, therefore in the direction of closing and opening.
The drive of the window lifter thus has a motor, a gear, a drivable cable, and a coupling to the drivable element (windowpane or vehicle windowpane). The transmission ratio of the worm gear can be, for example, 1:73 and the force acting on the window (excess force) is in the range of several 100 N. A large part of this force is required for moving the windowpane in the guide in order to overcome frictional and clamping resistances (stiff movements). In the area in which anti-trap protection must be active, namely, during the closing movement at a remaining opening of the window between 4 mm and 200 mm, it must be assured that the applied force of the drive, which can act as a clamping force on the trapped object after removal of the mechanical resistance forces, is less than 100 N. Nevertheless, still lower clamping forces are desirable.
It is common for the realization of anti-trap protection to monitor and limit the forces or torque transmitted overall by the drive motor. To this end, for example, DE 10 2010 013 597 B3 discloses incorporating spring elements in the drive kinematics, whose spring deflection is a measure for the transmitted force or the transmitted torque.
DE 10 231 450 A1 discloses detecting a trapping event by capturing and evaluating the movement path behavior of the window lifter drive. In particular a device for position and speed determination of the electrical drive by means of angle measurements on the drive motor is described therein.